1. Field of the Invention
The present invention relates to a water treatment pad (hereinafter referred to as a “pad”) used in drilling objects to be drilled, such as concrete structures, stone, base rock and steel structures, with a core drill.
2. Description of the Related Art
As a device for drilling concrete structures or the like, core drills are known. In drilling work with a core drill, the core drill in a rotating state is pressed against a predetermined drilling position and is moved downward to form holes. The drilling work will generate fragments and dust particles of concrete structures. To prevent them from scattering, the drilling work is generally performed while water is being supplied to drilling positions. The water supply is useful for cooling a core bit as well. The drilling work to be performed with such water supply conventionally uses water treatment pads as proposed in Japanese Patent Laid-Open Publication No. 2003-127131, Registered Utility Model No. 305895 Specification.
As shown in FIG. 13, a water treatment pad 100 is roughly cylindrical and is disposed on a drilling surface of a concrete structure or the like so as to surround a drilling position. Moreover, the water treatment pad has a drain outlet 102 (drain) on the side of the pad main body 101 to permit inside water to be discharged. Drilling with the water treatment pad 100 is performed while water supplied to a drilling position through a hollow portion in a core drill is being discharged from the drain 102. This permits fragments and dust particles generated during drilling to be discharged from a drilling position together with water to prevent the fragments and the like from scattering. For the purpose of drainage, in addition to natural drainage by attaching a hose to a drain outlet, there is proposed a system which performs forcible drainage by means of a suction force obtained by connecting a vacuum type cleaner (hereinafter referred to as a “cleaner”) for more efficient drainage.
As such a water treatment pad, a single-layered cylindrical pad as shown in FIG. 13 has been conventionally widely used, but such a pad has a problem of low drainage efficiency even with a cleaner. This is because a space in which the cleaner is sucked is under such a condition as to communicate with the atmosphere through an opening in the top of the pad (insertion opening in core drill), so that a pressure in the space becomes lower than the atmosphere however intensely suction is continued and drainage will become difficult.
Accordingly, as an improvement of the above-described water treatment pad, there has been known a pad of a double-layered structure as shown in FIG. 14. The water treatment pad 200 is formed with an inner wall 202 on a circumference between a drain outlet 101 and an opening 201 in the pad main body, and thus permits water to be sucked and discharged through a pressure space formed between an inner surface and the inner wall 202 of the pad main body. The pressure space facilitates formation of a negative pressure by suction of the cleaner, thus improving drainage efficiency.